It is known that light can be slowed down in the vicinity of resonances in dispersive materials. In order to reduce the group velocity (vg) of light coherently, there are two major approaches employing either electronic or optical resonances. In the electronic scheme, drastic slowing down and complete stopping of light pulses can be accomplished by converting optical signals into electronic coherences. The use of electronic states to coherently store the optical information, however, imposes severe constraints in the scheme, including narrow bandwidth, limited working wavelengths and strong temperature dependence.
While promising steps have been taken towards slowing light in solid-state media and semiconductor nanostructures operating at room temperature, “stopping” light completely and implementation of slow light structures on a chip including optoelectronic devices remains a great challenge. As a result of these obstacles, there has been great interest in pursuing alternative approaches utilizing optical resonances in photonic structures, such as microcavities, photonic crystals, and semiconductor waveguide ring resonators.
Recently, it was proposed that plasmonic structures and devices operating in the optical domain offer advantages for applications such as on-chip integration of optical circuits, surface or interface technology, and data storage. What makes the plasmonic structure unique is its potential for spatial confinement of electromagnetic energy within sub-wavelength dimensions over a wide spectral range.
Despite some advances in this field, there remains a need for an ultra-wide bandwidth slow-light system.